High-frequency amplifier, and transmission/reception system

ABSTRACT

In a high-frequency amplifier for amplifying transmission and reception signals, an integrated circuit area is reduced to reduce production costs. A high-frequency amplifier ( 101 ) includes a reception signal amplifying part ( 102 ), a transmission signal amplifying part ( 103 ), and a spiral inductor ( 104 ). An output of the reception signal amplifying part ( 102 ) is connected with an output of the transmission signal amplifying part ( 103 ) to be an output terminal OUT of the high-frequency amplifier ( 101 ). The single spiral inductor ( 104 ) is connected to the output terminal OUT. This spiral inductor ( 104 ) is used as a load common to the reception signal amplifying part ( 102 ) and the transmission signal amplifying part ( 103 ). Thereby, the area of the integrated circuit is reduced, and the production cost is reduced.

The present application is based on International ApplicationPCT/JP2006/307466, filed Apr. 7, 2006, which claims priority to JapanesePatent Application No. 2005-112429, filed Apr. 8, 2005, the entirecontents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a high-frequency amplifier foramplifying a reception signal and a transmission signal, and moreparticularly, to a small-area and low-cost high-frequency amplifier, anda transmission/reception system such as a handy phone in which thehigh-frequency amplifier is embedded.

BACKGROUND ART

In mobile communication systems, there is an increasing demand for ahigh-frequency signal processing integrated circuit which is directed totime division duplex (TDD) systems, such as wireless LAN, Bluetooth(trademark), and PHS (Personal Handyphone System), which performreception and transmission of radio signals in separated time zones.

The above-mentioned mobile communication systems are required to realizereductions in spaces and costs of integrated circuits becauseminiaturization and cost reduction of mobile communication devicesenhance popularization and convenience of the communication systems.

Currently, a front-end one-chip integrated circuit for processingcommunication signals from RF frequency to baseband frequency isrealized. FIG. 11 shows the construction of a high-frequency amplifierfor amplifying transmission and reception signals, which is included inthe conventional integrated circuit.

With reference to FIG. 11, a high-frequency amplifier 1101 includes alow-noise amplifier 1102 and a power amplifier 1103. The low-noiseamplifier 1102 amplifies a reception signal. The power amplifier 1103amplifies a transmission signal. Transistors 1104 and 1105 are providedin the low-noise amplifier 1102 and the power amplifier 1103,respectively. Spiral inductors 1106 and 1107 are provided in thelow-noise amplifier 1102 and the power amplifier 1103, respectively.

The transistors 1104 and 1105 are supplied with a DC power supply VDDthrough the spiral inductors 1106 and 1107, respectively.

A gate of the transistor 1104 is connected to a reception signal inputterminal IN_(RX) and to an end of a resistor R1. Another end of theresistor R1 is connected to a common terminal of atransmission/reception selector switch SW1. One of two terminals of theswitch SW1 is connected to ground that is shown by “∇” in FIG. 11, whilethe other terminal is connected to a positive side power supply terminalof a DC power supply Vbias1. A gate of the transistor 1105 is connectedto a transmission signal input terminal IN_(TX) and to an end of aresistor R2. Another end of the resistor R2 is connected to a commonterminal of a transmission/reception selector switch SW2. One of twoterminals of the switch SW2 is connected to ground that is shown by “∇”in FIG. 11, while the other terminal is connected to a positive sidepower supply terminal of a DC power supply Vbias2.

Negative side power supply terminals of the DC power supplies Vbias1 andVbias2 are connected to the ground. Further, sources of the transistors1104 and 1105 are connected to the ground.

Next, a description will be given of the fundamental operation of thehigh-frequency amplifier 1101 in the reception mode and the transmissionmode.

During the reception mode, a transmission/reception switching signal isinput to a transmission/reception switching control terminal S1 and to atransmission/reception switching control terminal S2. At this time, thetransmission/reception selector switch SW1 is connected to the terminalon the DC power supply Vbias1 side, and thereby the low-noise amplifier1102 turns on. On the other hand, the transmission/reception selectorswitch SW2 is connected to the terminal on the ground side, and therebythe power amplifier 1103 turns off. The turned-on low-noise amplifier1102 amplifies the reception signal inputted to the reception signalinput terminal IN_(RX), and outputs the signal to an output terminalOUT_(RX).

Further, during the transmission mode, the transmission/receptionswitching signal is input to the transmission/reception switchingcontrol terminal S1 and to the transmission/reception switching controlterminal S2. At this time, the transmission/reception selector switchSW1 is connected to the ground terminal, and thereby the low-noiseamplifier 1102 turns off. On the other hand, the transmission/receptionselector switch SW2 is connected to the DC power supply Vbias2, andthereby the power amplifier 1103 turns on. The turned-on power amplifier1103 amplifies the transmission signal inputted to the transmissionsignal input terminal IN_(TX), and outputs the signal to an outputterminal OUT_(TX).

In the conventional high-frequency amplifier, the spiral inductorsfabricated in the integrated circuit are used as loads of the low-noiseamplifier and the power amplifier, respectively (for example, refer toPatent Documents 1 and 2).

The reason is as follows. If the inductors are disposed outside theintegrated circuit, inductances of bonding wires and board wirings areparasitic on the inductors, and capacitances of ESD (electro-staticdischarge) protection elements and pads are parasitic on the inductors,and consequently, it becomes difficult to oscillate the loads of theamplifiers at desired frequencies.

Patent Document 1: Japanese Published Patent Application No. Hei.10-126174 (Page 20, FIG. 14)

Patent Document 2: Japanese Unexamined Patent Publication No.2004-516737 (Page 10, FIG. 1)

Problems to be Solved by the Invention

By the way, a spiral inductors in an integrated circuit occupies alarger area than other elements to obtain a desired inductance and alargest possible Q value. In the conventional high-frequency amplifiershown in FIG. 11, the two amplifiers use at least two spiral inductors1106 and 1107 as loads.

FIG. 12( a) shows a rough layout of the high-frequency amplifier shownin FIG. 11 which is fabricated in an ordinary CMOS process. In FIG. 12(a), the same reference numerals as those shown in FIG. 11 denote thesame elements. This spiral inductor is fabricated in a three-layerwiring process.

An area A of the spiral inductor 1107 is constituted as shown in FIG.12( b). That is, conductor patterns 1107 a and 1107 c of an uppermostwiring layer formed on a surface of a first interlayer isolation filmiso1 are connected to a conductor pattern 1107 d of an intermediatewiring layer formed on a surface of a second interlayer isolation filmiso2 via conductors filled in via-holes vh1 and vh2, and the conductorpatterns 1107 a and 1107 c sterically intersect with a conductor pattern1107 b formed on the surface of the first interlayer isolation filmiso1.

Further, in FIG. 12( a), a portion sandwiched by the upper-half poweramplifier 1103 and the lower-half low-noise amplifier 1102 correspondsto the sources of the transistors 1105 and 1104, i.e., the ground GND.

In this layout, the area occupied by the two spiral inductors eachhaving an inductance of 6 nH is 0.32 mm², while the area of the entirelayout of the high-frequency amplifier 1101 is 0.60 mm². Accordingly,the two spiral inductors occupy 53% of the whole layout area.

Generally, the above-mentioned amplifiers are multistage-connected toobtain a high gain. Assuming that the number of stages of the low-noiseamplifiers is m and the number of stages of the power amplifiers is n(m,n: positive integers) in this multistage connection, the number ofspiral inductors becomes m+n. When the low-noise amplifiers and thepower amplifiers are constructed by differential type amplifiers, thenumber of spiral inductors becomes 2(m+n).

As a result, the area of the integrated circuit increases, and the costalso increases.

It is generally known that miniaturization of an integrated circuitleads to a reduction in production cost of a semiconductor chip as wellas a reduction in a semiconductor chip mounting area.

The present invention is made to solve the above-mentioned problems andhas for its object to provide a high-frequency amplifier for amplifyingtransmission and reception signals, which miniaturizes the area of anintegrated circuit in which the amplifier is mounted, and reduces theproduction cost of the integrated circuit, and a transmission/receptionsystem including the high-frequency amplifier.

Measures to Solve the Problems

According to Claim 1 of the present invention, there is provided ahigh-frequency amplifier including a reception signal amplifying part, atransmission signal amplifying part, and an inductor; wherein thereception signal amplifying part has a reception signal input terminal,and a first transmission/reception switching control terminal; thetransmission signal amplifying part has a transmission signal inputterminal, and a second transmission/reception switching controlterminal; a common output terminal to which an output of the receptionsignal amplifying part and an output of the transmission signalamplifying part are connected is provided; switching of operations ofthe reception signal amplifying part and the transmission signalamplifying part is carried out such that, during a reception mode,control signals are input to the first transmission/reception switchingcontrol terminal and to the second transmission/reception switchingcontrol terminal, whereby the transmission signal amplifying part isturned off and the reception signal amplifying part is turned on toamplify a reception signal that is inputted from the reception signalinput terminal, and during a transmission mode, control signals areinput to the first transmission/reception switching control terminal andto the second transmission/reception switching control terminal, wherebythe reception signal amplifying part is turned off and the transmissionsignal amplifying part is turned on to amplify a transmission signalthat is inputted from the transmission signal input terminal; and theinductor is connected between a DC power supply terminal and the outputterminal as a load that is common to the reception signal amplifyingpart and the transmission signal amplifying part.

According to the high-frequency amplifier of Claim 1, the receptionsignal amplifying part is turned on during the reception mode, while thetransmission signal amplifying part is turned on during the transmissionmode. Therefore, a single inductor can be used as a load that is commonto the reception signal amplifying part and the transmission signalamplifying part.

According to Claim 2 of the present invention, there is provided ahigh-frequency amplifier including a reception signal amplifying part, atransmission signal amplifying part, an inductor, and a transistor;wherein the reception signal amplifying part has a reception signalinput terminal, and a first transmission/reception switching controlterminal; the transmission signal amplifying part has a transmissionsignal input terminal, and a second transmission/reception switchingcontrol terminal; an output of the reception signal amplifying part andan output of the transmission signal amplifying part are connected tothe transistor; switching of operations of the reception signalamplifying part and the transmission signal amplifying part is carriedout such that, during a reception mode, control signals are input to thefirst transmission/reception switching control terminal and to thesecond transmission/reception switching control terminal, whereby thetransmission signal amplifying part is turned off, and the receptionsignal amplifying part is turned on to amplify a reception signal thatis inputted from the reception signal input terminal, and during atransmission mode, control signals are input to the firsttransmission/reception switching control terminal and to the secondtransmission/reception switching control terminal, whereby the receptionsignal amplifying part is turned off, and the transmission signalamplifying part is turned on to amplify a transmission signal that isinputted from the transmission signal input terminal; the inductor isconnected between a DC power supply terminal and the transistor as aload that is common to the reception signal amplifying part and thetransmission signal amplifying part; and an output terminal is providedat a connection point of the inductor and the transistor.

According to the high-frequency amplifier of Claim 2, cascadetransistors are provided between the inductor and the outputs of thereception signal amplifying part and the transmission signal amplifyingpart, respectively, and the reception signal amplifying part is turnedon during the reception mode, while the transmission signal amplifyingpart is turned on during the transmission mode. Therefore, a singleinductor can be used as a load that is common to the reception signalamplifying part and the transmission signal amplifying part, therebyreducing a parasitic capacitance at the output terminal.

According to Claim 3 of the present invention, the high-frequencyamplifier defined in Claim 1 or 2 further includes a switch and atransmission signal output terminal; the switch is connected between theoutput terminal and the transmission signal output terminal; during thereception mode, the switch is turned off, whereby the reception signalinputted from the reception signal input terminal is amplified andtransmitted to the output terminal; and during the transmission mode,the switch is turned on, whereby the transmission signal inputted fromthe transmission signal input terminal is amplified and transmitted tothe transmission signal output terminal.

According to the high-frequency amplifier of Claim 3, since the outputterminals exclusively for the transmission mode and the reception modeare provided, the reception signal amplified during the reception modeis prevented from leaking to an antenna.

According to Claim 4 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, the reception signal amplifying parthas a transistor for amplifying the reception signal.

According to the high-frequency amplifier of Claim 4, in thehigh-frequency amplifier defined in Claim 1 or 2, the reception signalamplifying part may be constituted so as to have a transistor foramplifying the reception signal.

According to Claim 5 of the present invention, in the high-frequencyamplifier defined in Claim 4, the transistor of the reception signalamplifying part is optimized to realize noise matching.

According to the high-frequency amplifier of Claim 5, in thehigh-frequency amplifier defined in Claim 4, the transistor of thereception signal amplifying part may be optimized to realize noisematching.

According to Claim 6 of the present invention, in the high-frequencyamplifier defined in Claim 4, the transistor of the reception signalamplifying part is optimized to realize gain matching.

According to the high-frequency amplifier of Claim 6, in thehigh-frequency amplifier defined in Claim 4, the transistor of thereception signal amplifying part may be optimized to realize gainmatching.

According to Claim 7 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, the transmission signal amplifyingpart has a transistor for amplifying power.

According to the high-frequency amplifier of Claim 7, in thehigh-frequency amplifier defined in Claim 1 or 2, the transmissionsignal amplifying part may have a transistor for amplifying power.

According to Claim 8 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, the inductor comprises a spiralinductor that is mounted in an integrated circuit.

According to the high-frequency amplifier of Claim 8, the space occupiedby the inductor in the integrated circuit can be reduced.

According to Claim 9 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, the reception signal amplifying part,the transmission signal amplifying part, and the inductor are mounted onthe same integrated circuit.

According to the high-frequency amplifier of Claim 9, in thehigh-frequency amplifier defined in Claim 1 or 2, a single inductor tobe a load that is common to the reception signal amplifying part and thetransmission signal amplifying part is provided, and the receptionsignal amplifying part, the transmission signal amplifying part, and theinductor are mounted on the same integrated circuit. Therefore, thespace occupied by the inductor in the integrated circuit can be reduced,thereby reducing the scale of the integrated circuit.

According to Claim 10 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, the inductor comprises a spiralinductor that is mounted in a module.

According to the high-frequency amplifier of Claim 10, the spaceoccupied by the inductor in the module can be reduced.

According to Claim 11 of the present invention, there is provided ahigh-frequency amplifier comprising two pieces of high-frequencyamplifiers defined in Claim 1 or 2, and the amplifiers amplify adifferential reception signal and a differential transmission signal,respectively.

According to the high-frequency amplifier of Claim 11, two pieces ofhigh-frequency amplifiers defined in Claim 1 or 2 may be provided toamplify a differential reception signal and a differential transmissionsignal, respectively.

According to Claim 12 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, each of transistors constituting thehigh-frequency amplifier is any of a MOSFET, a MESFET, a JFET, a HEMT, abipolar junction transistor, and a heterojunction transistor, or acombination of some of these transistors.

According to the high-frequency amplifier of Claim 12, each of thetransistors constituting the high-frequency amplifier defined in Claim 1or 2 may be any of a MOSFET, a MESFET, a JFET, a HEMT, a bipolarjunction transistor, and a heterojunction transistor, or a combinationof some of these transistors.

According to Claim 13 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, each of transistors constituting thehigh-frequency amplifier comprises any of silicon, silicon-germanium,and III-V compound semiconductor.

According to the high-frequency amplifier of Claim 13, each of thetransistors constituting the high-frequency amplifier defined in Claim 1or 2 may comprise any of silicon, silicon-germanium, and III-V compoundsemiconductor.

According to Claim 14 of the present invention, in the high-frequencyamplifier defined in Claims 1 or 2, the reception signal amplifying parthas a transistor for amplifying the reception signal, and a firstvariable voltage supply that can vary a voltage applied between a gateof the transistor and the ground; the transmission signal amplifyingpart has a transistor for amplifying power, and a second variablevoltage supply that can vary a voltage applied to a gate of thetransistor and the ground; the first transmission/reception switchingcontrol terminal is connected to the first variable voltage supply; thesecond transmission/reception switching control terminal is connected tothe second variable voltage supply; during the reception mode, controlsignals are input to the first transmission/reception switching controlterminal and to the second transmission/reception switching controlterminal, whereby the transmission signal amplifying part is almostturned off, and the reception signal amplifying part is turned on toamplify the reception signal inputted from the reception signal inputterminal at low noise.

According to the high-frequency amplifier of Claim 14, it is possible toamplify the reception signal at low noise by not only turning on thereception signal amplifying part during the reception mode but alsosetting the transmission signal amplifying part in the on state that isalmost close to the off state.

According to Claim 15 of the present invention, the high-frequencyamplifier defined in Claim 1 or 2 further includes a switch disposedbetween the output terminal and the reception signal input terminal, andthe switch is turned on when the reception signal has a large amplitude.

According to the high-frequency amplifier of Claim 15, when a receptionsignal of a large amplitude is inputted, the switch is turned on and thereception signal passes through the high-frequency amplifier withoutbeing amplified in the amplifier, whereby saturation of the receptionsignal can be suppressed.

According to Claim 16 of the present invention, in the high-frequencyamplifier defined in Claim 1 or 2, when a capacitance that is requiredbetween the output terminal and the ground by the high-frequencyamplifier is deficient due to a parasitic capacitance at the outputterminal, a capacitance having a capacitance value corresponding to thedeficit is connected.

According to the high-frequency amplifier of Claim 16, when acapacitance required by the high-frequency amplifier is deficient due tothe parasitic capacitance, a capacitance equivalent to the deficit isadded, whereby the high-frequency amplifier can have the predeterminedcapacitance.

According to Claim 17 of the present invention, the high-frequencyamplifier defined in Claim 1 or 2 further includes switches disposedbetween the reception signal input terminal, the transmission signalinput terminal and the ground, respectively, and the switch which isdisposed at the side where the reception signal amplifying part or thetransmission signal amplifying part is turned off, is turned on.

According to the high-frequency amplifier of Claim 17, since the signalinput terminal of either the reception signal amplifying part or thetransmission signal amplifying part, which is desired to be turned off,is grounded, amplification of the reception signal or the transmissionsignal by the reception signal amplifying part or the transmissionsignal amplifying part can be reliably turned off.

According to Claim 18 of the present invention, the high-frequencyamplifier defined in Claim 1 or 2 further includes a switch, aninput/output terminal, and first and second capacitances; aseries-connected body comprising said switch and said first capacitanceis connected between a node to which the output terminal is connected,and the input/output terminal; the input/output terminal is connectedthrough the second capacitance to a node to which the transmissionsignal input terminal should be connected; during the reception mode,said switch is turned off, and the reception signal inputted to theinput/output terminal is amplified and transmitted to the outputterminal; and during the transmission mode, said switch is turned on,and the transmission signal inputted from the transmission signal inputterminal is amplified and transmitted to the input/output terminal.

According to the high-frequency amplifier of Claim 18, the outputterminal for the amplified transmission signal and the input terminalfor the reception signal can be consolidated to an input/outputterminal.

According to Claim 19 of the present invention, there is provided atransmission/reception system having a transmission/reception unit fortransmitting and receiving a high-frequency signal, which systemincludes a high-frequency amplifier defined in Claim 1 or 2 and operatesaccording to a time-division duplex communication scheme.

According to the transmission/reception system of Claim 19, the systemhaving a transmission/reception unit for transmitting and receiving ahigh-frequency signal includes the high-frequency amplifier defined inClaim 1 or 2, and operates according to the time-division duplexcommunication scheme. Therefore, the transmission/reception unit canshare the same inductor.

According to Claim 20 of the present invention, there is provided atransmission/reception system having a transmission/reception unit fortransmitting and receiving a high-frequency signal, which systemincludes a plurality of high-frequency amplifiers defined in Claim 1 or2, and is capable of setting whether the plural high-frequencyamplifiers are simultaneously switched between the transmission mode andthe reception mode, or some of them are in the transmission mode whilethe others are in the reception mode.

According to the transmission/reception system of Claim 20, the sametransmission/reception system can be used as either a MIMO transceiveror an FDD transceiver by changing the setting.

EFFECTS OF THE INVENTION

According to the present invention, in a high-frequency amplifier foramplifying a reception signal and a transmission signal, only one spiralinductor is used as a load of the amplifier, thereby realizing asmall-area and low-cost high-frequency amplifier.

Further, the high-frequency amplifier is constituted such that, duringthe reception mode, the reception signal amplifying part is turned onand the transmission signal amplifying part is set in an on state thatis almost close to off, thereby realizing low-noise amplification forthe reception signal.

Further, in a transmission/reception system including a high-frequencyamplifier for amplifying a reception signal and a transmission signal,the high-frequency amplifier is constituted so as to include only onespiral inductor to be used as a load, thereby realizing a small-area andlow-cost transmission/reception system.

Furthermore, the transmission/reception system includes a plurality ofhigh-frequency amplifiers for amplifying a reception signal and atransmission signal, each having only one spiral inductor to be used asa load, and the system is able to set whether the plural high-frequencyamplifiers are simultaneously switched between the transmission mode andthe reception mode, or some of them are in the transmission mode whilethe others are in the reception mode. Therefore, the singletransmission/reception system can be used as either a MIMO transceiveror an FDD transceiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the construction of a high-frequencyamplifier 101 according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the construction of a high-frequencyamplifier 101 as a first example of the first embodiment.

FIG. 3( a) is a diagram illustrating the circuit construction of theentirety of a high-frequency amplifier 101 b as a second example of thefirst embodiment.

FIG. 3( b) is a diagram illustrating a switch for short-circuiting whichis provided at a DC power supply of the high-frequency amplifier 101 baccording to the first embodiment.

FIG. 4 is a diagram illustrating the construction of a high-frequencyamplifier 101 c as a third example of the first embodiment.

FIG. 5 is a diagram illustrating the construction of a high-frequencyamplifier 501 according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating the construction of a high-frequencyamplifier 501 a as a first example of the second embodiment.

FIG. 7 is a layout diagram illustrating the outline of thehigh-frequency amplifier 501 a as the first example of the secondembodiment.

FIG. 8 is a diagram illustrating the construction of a high-frequencyamplifier 501 b as a second example of the second embodiment.

FIG. 9 is a diagram illustrating the construction of atransmission/reception system 901 according to a third embodiment of thepresent invention.

FIG. 10 is a diagram illustrating the construction of atransmission/reception system 901 a as a second example of the thirdembodiment.

FIG. 11 is a diagram illustrating the construction of a conventionalhigh-frequency amplifier 1101.

FIG. 12( a) is a plan view of a layout illustrating the outline of theconventional high-frequency amplifier 1101.

FIG. 12( b) is a cross-sectional view taken along a line B-B′ in thelayout illustrating the outline of the conventional high-frequencyamplifier 1101.

FIG. 13( a) is a diagram illustrating the construction of ahigh-frequency amplifier 1301 according to a fourth embodiment of thepresent invention.

FIG. 13( b) is a diagram illustrating the specific construction of thehigh-frequency amplifier 1301 according to the fourth embodiment.

FIG. 14( a) is a diagram illustrating the case where the high-frequencyamplifier according to the fourth embodiment is operated as a MIMOtransceiver.

FIG. 14( b) is a diagram illustrating the case where the high-frequencyamplifier according to the fourth embodiment is operated as an FDDtransceiver.

FIG. 15( a) is a diagram illustrating the construction of ahigh-frequency amplifier 501 c as a first example of a fifth embodimentof the present invention.

FIG. 15( b) is a diagram illustrating the construction of ahigh-frequency amplifier 501 d as a second example of the fifthembodiment.

FIG. 15( c) is a diagram illustrating the construction of ahigh-frequency amplifier 501 e as a third example of the fifthembodiment.

FIG. 16( a) is a diagram illustrating the construction of ahigh-frequency amplifier 501 f as a first example of a sixth embodimentof the present invention.

FIG. 16( b) is a diagram illustrating the construction of ahigh-frequency amplifier 501 g as a second example of the sixthembodiment.

FIG. 16( c) is a diagram illustrating the high-frequency amplifier 501 gas the second example of the sixth embodiment and a next-stage amplifier501 g 1.

FIG. 17( a) is a diagram illustrating a high-frequency amplifier 101 cas a first example of a seventh embodiment of the present invention.

FIG. 17( b) is a diagram illustrating a high-frequency amplifier 501(b)as a second example of the seventh embodiment.

DESCRIPTION OF REFERENCE NUMERALS

-   -   50 . . . control unit    -   70 . . . reception signal amplitude detection unit    -   101, 101 a, 101 b, 101 c, 501, 501 a, 501 b, 501 c, 501 d, 501        f, 501 g, 501 g 1, 1101, 1301, 1301 a, 1301 b . . .        high-frequency amplifier    -   102, 1302 a, 1302 b . . . reception signal amplifying part    -   103, 1303 a, 1303 b . . . transmission signal amplifying part    -   104, 1106, 1107, 1304 a, 1304 b . . . spiral inductor    -   201, 202, 301, 302, 303, 304, 502, 502 a, 502 b, 601, 602, 801,        801 a, 801 b, 802, 802 a, 802 b, 1104, 1105 . . . transistor    -   901, 901 a, 901 b, 1401 a, 1401 b . . . transmission/reception        system    -   901 d . . . package    -   902, 902 a, 902 b, 1001 . . . transmission/reception integrated        circuit for communication    -   903, 903 a, 903 b . . . antenna    -   904, 904 a, 904 b . . . RF filter    -   905, 905 a, 905 b, 1002, 1003 . . . transmission/reception        selector switch    -   906, 906 a, 906 b . . . input matching circuit    -   907, 907 a, 907 b . . . output matching circuit    -   908, 908 a, 908 b . . . reception mixer    -   909, 909 a, 909 b . . . transmission mixer    -   910, 910 a, 910 b . . . frequency synthesizer    -   911, 911 a, 911 b . . . reception filter    -   912, 912 a, 912 b . . . transmission filter    -   913, 913 a, 913 b . . . A/D converter    -   914, 914 a, 914 b . . . D/A converter    -   915, 915 a, 915 b, 915 d . . . digital signal processor    -   1102 . . . low-noise amplifier    -   1103 . . . power amplifier    -   IN_(RX), IN_(RXa), IN_(RXb) . . . reception signal input        terminal    -   IN_(TX), IN_(TXa), IN_(TXb) . . . transmission signal input        terminal    -   S1, S1 a, S1 b, S2, S2 a, S2 b . . . transmission/reception        switching control terminal    -   OUT, OUTa, OUTb, OUT_(RX), OUT_(RXa), OUT_(RXb) . . . output        terminal    -   VDD . . . DC power supply    -   Sw1, Sw1 a, Sw1 b, SW2, SW2 a, SW2 b, SW3, SW4, SW5, SW5 a, SW5        b, SW6, SW7, SW8 . . . switch    -   OUT_(TX), OUT_(TXa), OUT_(TXb) . . . transmission signal output        terminal    -   CF . . . parasitic capacitance    -   Vc . . . variable capacitance element    -   Vvr1, Vvr2 . . . variable voltage supply    -   CA, CA1, CA2, CA3 . . . capacitance    -   SA1, SA2, SA3 . . . switch    -   R1, R2 . . . resistor    -   Vbias1, Vbias2 . . . DC power supply

BEST MODE TO EXECUTE THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

Embodiment 1

FIG. 1 shows the construction of a high-frequency amplifier 101according to a first embodiment of the present invention.

In FIG. 1, the high-frequency amplifier 101 includes a reception signalamplifying part 102, a transmission signal amplifying part 103, a spiralinductor 104, and an output terminal OUT.

The reception signal amplifying part 102 includes atransmission/reception switching control terminal S1, and a receptionsignal input terminal IN_(RX). The transmission signal amplifying part103 includes a transmission/reception switching control terminal S2, anda transmission signal input terminal IN_(TX). The reception signalamplifying part 102 and the transmission signal amplifying part 103 aresupplied with a DC power supply VDD via the same spiral inductor 104.

The output terminal OUT is connected to a node of the spiral inductor104 on the opposite side from the DC power supply VDD.

During the reception mode, transmission/reception switching controlsignals from a control unit 50 are applied to the transmission/receptionswitching control terminal S1 and to the transmission/receptionswitching control terminal S2, whereby the reception signal amplifyingpart 102 is turned on while the transmission signal amplifying part 103is turned off.

A reception signal is input through the reception signal input terminalIN_(RX), and the reception signal amplifying part 102 amplifies thereception signal with the spiral inductor 104 being a load, and outputsthe amplified signal to the output terminal OUT which is common for thetransmission and reception modes.

Conversely, during the transmission mode, transmission/receptionswitching control signals are applied to the transmission/receptionswitching control terminal S1 and to the transmission/receptionswitching control terminal S2, whereby the reception signal amplifyingpart 102 is turned off while the transmission signal amplifying part 103is turned on. A transmission signal is input through the transmissionsignal input terminal IN_(TX), and the transmission signal amplifyingpart 103 amplifies the transmission signal with the spiral inductor 104being a load, and outputs the amplified signal to the output terminalOUT which is common for the transmission and reception modes.

Time-division duplex communication is achieved by alternately performingthe reception mode and the transmission mode.

During the respective modes, the spiral inductor 104 functions as a loadthat is common to the reception signal amplifying part 102 and thetransmission signal amplifying part 103.

Therefore, only one spiral inductor is provided in this first embodimentwhile two spiral inductors are required in the conventionalhigh-frequency amplifier 1101 shown in FIG. 11. Thereby, the area of theintegrated circuit is reduced, and the production cost thereof is alsoreduced.

A resonance frequency of the load of the high-frequency amplifier 101 isdetermined according to a capacitance C_(POUT) at the output terminalOUT, and the value of an inductance L of the spiral inductor 104.

The capacitance C_(POUT) at the output terminal OUT is expressed by asum of a parasitic capacitance C_(PRX) in the output of the receptionsignal amplifying part 102, a parasitic capacitance C_(PTX) in theoutput of the transmission signal amplifying part 103, an external loadcapacitance C_(PL) of the high-frequency amplifier 101 connected to theoutput terminal OUT, and a parasitic capacitance C_(PIND) of the spiralinductor 104. That is,CP _(OUT) =C _(PRX) +C _(PTX) +C _(PL) +C _(PIND)

Accordingly, the resonance frequency f₀ of the load of thehigh-frequency amplifier 101 is expressed byf ₀=1/(2π(LC _(POUT))^(0.5))

FIG. 2 shows the construction of a high-frequency amplifier 101 a whichis a first example of the high-frequency amplifier 101 of the firstembodiment.

With reference to FIG. 2, in the high-frequency amplifier 101 a, theconstructions of the reception signal amplifying part 102 and thetransmission signal amplifying part 103 of the high-frequency amplifier101 shown in FIG. 1 are implemented by transistors 201 and 202,resistors R1 and R2, switches SW1 and SW2, and DC power supplies Vbias1and Vbias2, respectively.

Hereinafter, it is assumed an N channel MOSFET (hereinafter referred toas “NMOSFET”) is used as each transistor. A drain of the transistor 201is connected to one end of the spiral inductor 104, the output terminalOUT, and a drain of the transistor 202. Sources of the transistors 201and 202 are connected to the ground. The other end of the spiralinductor 104 is connected to the DC current source VDD.

A gate of the transistor 201 is connected to the reception signal inputterminal IN_(RX) of the high-frequency amplifier 101 a. The gate of thetransistor 201 is also connected to a common terminal of thetransmission/reception selector switch SW1 through the resistor R1. Oneof two terminals of the switch SW1 is connected to the ground, while theother end is connected to the positive side power supply terminal of theDC power supply Vbias1.

A gate of the transistor 202 is connected to the transmission signalinput terminal IN_(TX) of the high-frequency amplifier 101 a. The gateof the transistor 202 is also connected to a common terminal of thetransmission/reception selector switch SW2 through the resistor R2. Oneof two terminals of the switch SW2 is connected to the ground, while theother end is connected to the positive side power supply terminal of theDC power supply Vbias2.

The negative side power supply terminals of the DC power supplies Vbias1and Vbias2 are connected to the ground.

In the reception mode, transmission/reception switching control signalsfrom the control unit 50 shown in FIG. 1 are input to thetransmission/reception switching control terminal S1 and to thetransmission/reception switching control terminal S2, and the switch SW1is connected to the terminal on the bias DC power supply Vbias1 side,and thereby the transistor 201 turns on, while the switch SW2 isconnected to the terminal on the ground side, and thereby the transistor202 turns off. Thereby, only the reception signal amplifying part(low-noise amplifier) 102 is turned on.

In the transmission mode, the states of the switches SW1 and SW2 and thestates of the transistors 201 and 202 are exchanged, respectively.Thereby, only the transmission signal amplifying part (power amplifier)103 is turned on. The transmission/reception selector switches SW1 andSW2 may have other constructions than those mentioned above so long asthey can turn on and off the transistors 201 and 202.

FIG. 3 shows the construction of a high-frequency amplifier 101 b as asecond example of the high-frequency amplifier 101 according to thesecond embodiment.

With reference to FIG. 3( a), in the high-frequency amplifier 101 b, theconstructions of the reception signal amplifying part 102 and thetransmission signal amplifying part 103 of the high-frequency amplifier101 shown in FIG. 1 are implemented by NMOS transistors 301, 302, 303,and 304, resistors R1 and R2, switches SW3 and SW4, and DC powersupplies Vbias1, Vbias2, Vbias3, and Vbias4, respectively.

A drain of the transistor 301 is connected to a source of the transistor302. A gate of the transistor 301 is connected to the reception signalinput terminal IN_(RX) of the high-frequency amplifier 101 b. The gateof the transistor 301 is also connected to the positive side powersupply terminal of the DC power supply Vbias1 via the resistor R1. Asource of the transistor 301 is connected to the ground.

A drain of the transistor 302 is connected to an end of the spiralinductor 104, the output terminal OUT, and a drain of the transistor304. A gate of the transistor 302 is connected to a common terminal ofthe transmission/reception selector switch SW3. One of two terminals ofthe switch SW3 is connected to the ground, while the other terminal isconnected to the positive side power supply terminal of the DC currentsupply Vbias3. The other end of the spiral inductor 104 is connected tothe DC power supply VDD.

Similarly, a drain of the transistor 303 is connected to a source of thetransistor 304. A gate of the transistor 303 is connected to thetransmission signal input terminal IN_(TX) of the high-frequencyamplifier 101 b. The gate of the transistor 303 is also connected to thepositive side power supply terminal of the DC power supply Vbias2 viathe resistor R2. A source of the transistor 303 is connected to theground.

A gate of the transistor 304 is connected to a common terminal of thetransmission/reception selector switch SW4. One of two terminals of theswitch SW4 is connected to the ground, while the other end is connectedto the positive side power supply terminal of the DC power supplyVbias4.

The negative side power supply terminals of the DC power suppliesVbias1, Vbias2, Vbias3, and Vbias4 are grounded.

In the reception mode, transmission/reception switching control signalsfrom the control unit 50 shown in FIG. 1 are input to thetransmission/reception switching control terminal S1 and to thetransmission/reception switching control terminal S2, whereby the switchSW3 is connected to the terminal on the bias DC power supply Vbias3side, and thereby the transistor 302 turns on, while the switch SW4 isconnected to the terminal on the ground side, and thereby the transistor304 turns off.

During the transmission mode, the states of the switches SW3 and SW4 andthe states of the transistors 302 and 304 are exchanged, respectively.

The high-frequency amplifier 101 b shown in FIG. 3 is different from thehigh-frequency amplifier 101 a shown in FIG. 2 in that the transistorsof the reception signal amplifying part 102 (transmission signalamplifying part 103) are cascade type transistors, and thetransmission/reception selector switches SW3 and SW4 are connected tothe gates of the cascade transistors, respectively.

In the high-frequency amplifier 101 b, only either the transistors ofthe reception signal amplifying part 102 or the transistors of thetransmission signal amplifying part 103 may be cascade type transistors.

Further, as shown in FIG. 3( b), a switch SW5 may be disposed betweenthe resistor R1 and the DC power supply Vbias1 that biases the gate ofthe transistor 301 to make the bias voltage zero when the transistor 301is turned off. Further, a switch similar to the switch SW5 may bedisposed on the transistor 303 side.

FIG. 4 shows the construction of a high-frequency amplifier 101 c as athird example of the high-frequency amplifier 101 according to the firstembodiment.

In FIG. 4, the high-frequency amplifier 101 c is different from thehigh-frequency amplifier 101 b shown in FIG. 3 in that it has outputterminals for the transmission mode and the reception mode,respectively.

In the high-frequency amplifier 101 b shown in FIG. 3, the signalsoutputted from the reception signal amplifying part 102 and thetransmission signal amplifying part 103 use the common output terminalOUT. The amplified reception signal is connected to the circuits in thenext stage, such as an amplifier, a mixer, and a filter, and inputimpedances of these circuits are usually high.

On the other hand, the amplified transmission signal is transmitted toan antenna, and the impedance of the antenna is usually as low as 50Ω.Further, even when an output matching circuit is connected between thehigh-frequency amplifier 101 b and the antenna, the input impedance ofthe output matching circuit is low.

In the high-frequency amplifier 101 c shown in FIG. 4, a transmissionsignal output terminal OUT_(TX) for connecting the antenna or the outputmatching circuit with the high-frequency amplifier 101 b is newly added,and a switch S6 is connected between the transmission signal outputterminal OUT_(TX) and the output terminal OUT_(RX) (corresponding to OUTin FIG. 3).

During the reception mode, the switch SW6 is opened, and the amplifierreception signal is outputted from the output terminal OUT_(RX).

During the transmission mode, the switch SW6 is short-circuited, and theamplified signal is outputted from the transmission signal outputterminal OUT_(TX).

Thereby, the reception signal that is amplified during the receptionmode is prevented from leaking into the antenna.

As described above, according to the first embodiment, two spiralinductors to be connected as loads between the power supply terminal andthe output terminal of the low-noise amplifier that amplifies areception signal when performing communication by the time-divisionduplex scheme and between the power supply terminal and the outputterminal of the power amplifier that amplifies the transmission signal,are unified. Therefore, when the high-frequency amplifier is constitutedas an integrated circuit, the ratio of the spiral inductor to thesubstrate area of the integrated circuit can be reduced, and thereby theintegrated circuit can be miniaturized, resulting in a high-frequencyamplifier that can be manufactured at reduced cost.

While in this first embodiment the high-frequency amplifier 101 isprovided with two transmission/reception switching control terminals,the number of the transmission/reception switching control terminals maybe one or more so long as it can perform operational switching betweenthe reception signal amplifying part 102 and the transmission signalamplifying part 103.

Further, while the switch SW6 has one transmission/reception switchingcontrol terminal (S1 or S2), the switch SW6 may have twotransmission/reception switching control terminals (S1 and S2).

Further, in this first embodiment, inductors may be used in place of theresistors R1 and R2.

Further, while in this first embodiment the high-frequency amplifier 101amplifies a single-phase transmission signal and a single-phasereception signal, two pieces of high-frequency amplifiers 101 may beprovided to amplify a differential transmission signal and adifferential reception signal.

Further, in the reception signal amplifying part, in order to achievematching of either or both of noise and gain, an inductor, or aresistor, or a capacitor may be connected to either or both of the gateand source of the NMOS transistor.

Further, while in this first embodiment the reception signal amplifyingpart 102 and the transmission signal amplifying part 103 include onlythe NMOS transistors, the reception signal amplifying part 102 and thetransmission signal amplifying part 103 may be constituted ashigh-frequency amplifiers including only PMOS transistors by invertingthe polarity of the circuit so that those skilled in the art can easilyunderstand.

Further, while in this first embodiment MOSFETs are used as thetransistors, the transistors may be implemented by any of MESFETs,JFETs, HEMTs, bipolar junction transistors, and heterojunctiontransistors, or a combination of some of these transistors.

Further, the transistors in the first embodiment may be implemented byany of silicon, silicon-germanium, and III-V compound semiconductor.

Furthermore, the spiral inductor 104 according to the first embodimentincludes inductors in the integrated circuit and in a package or moduleincluding the integrated circuit. The point is that the high-frequencyamplifier 101 should be constituted such that the reception signalamplifying part 102 and the transmission signal amplifying part 103share one inductor as a common load, and a switch for alternatelyturning on and off the reception signal amplifying part 102 and thetransmission signal amplifying part 103 is provided.

Embodiment 2

FIG. 5 shows the construction of a high-frequency amplifier 501according to a second embodiment of the present invention.

With reference to FIG. 5, the high-frequency amplifier 501 includes atransmission signal amplifying part 102, a transmission signalamplifying part 103, a spiral inductor 104, an output terminal OUT, atransistor 502, and a DC power supply Vbias5. The reception signalamplifying part 102 includes a transmission/reception switching controlterminal S1, and a reception signal input terminal IN_(RX). Thetransmission signal amplifying part 103 includes atransmission/reception switching control terminal S2, and a transmissionsignal input terminal IN_(TX).

A drain of the transistor 502 is connected to the output terminal OUT,and to the DC power supply VDD via the spiral inductor 104. A source ofthe transistor 502 is connected to the outputs of the reception signalamplifying part 102 and the transmission signal amplifying part 103. Agate of the transistor 502 is connected to a positive side power supplyterminal of the DC power supply Vbias5.

The negative side power supply terminal of the DC power supply Vbias5 isconnected to the ground.

In the respective modes of reception and transmission, the operations ofthe reception signal amplifying part 102 and the transmission signalamplifying part 103 are identical to the operations of those in thehigh-frequency amplifier 101 shown in FIG. 1 according to the firstembodiment. The high-frequency amplifier 501 is different from thehigh-frequency amplifier 101 in that the transistor 502 is connected tothe outputs of the reception signal amplifier 102 and the transmissionsignal amplifier 103.

A resonance frequency of the load of the high-frequency amplifier 501 isdetermined according to a capacitance C_(POUT) at the output terminalOUT, and an inductance L of the spiral inductor 104. The capacitanceC_(POUT) at the output terminal OUT is expressed by a sum of a parasiticcapacitance C_(PCAS) of the drain of the transistor 502, an externalload capacitance C_(PL) of the high-frequency amplifier 101 connected tothe output terminal OUT, and a parasitic capacitance C_(PIND) of thespiral inductor 104. That is,CP _(OUT) =C _(PCAS) +C _(PL) +C _(PIND)

Accordingly, the resonance frequency f₀ of the load of thehigh-frequency amplifier 501 is expressed byf ₀=1/(2π(LC _(POUT))^(0.5))

The transistor 502 functions as a cascade stage transistor. Accordingly,when the parasitic capacitances in the outputs of the receiving signalamplifying part 102 and transmission signal amplifying part 103 in thehigh-frequency amplifier 101 of the first embodiment are equal to thosein the high-frequency amplifier 501 of the second embodiment, theparasitic capacitance in the output terminal OUT of the high-frequencyamplifier 501 is smaller than that of the high-frequency amplifier 101.

When the high-frequency amplifier 501 and the high-frequency amplifier101 of the first embodiment are operated with the same resonancefrequency, the inductance L of the spiral inductor 104 can be increased.Further, a loss due to leakage through the parasitic capacitance at theoutput terminal OUT can be reduced. Accordingly, the gain of thehigh-frequency amplifier can be increased.

FIG. 6 shows the construction of a high-frequency amplifier 501 a as afirst example of the high-frequency amplifier 501 according to thesecond embodiment of the present invention.

With reference to FIG. 6, in the high-frequency amplifier 501 a, theconstructions of the reception signal amplifying part 102 and thetransmission signal amplifying part 103 of the high-frequency amplifier501 shown in FIG. 5 are implemented by NMOS transistors 601 and 602,resistors R1 and R2, switches SW1 and SW2, and DC power supplies Vbias1and Vbias2, respectively.

A drain of the transistor 601 is connected to a source of the transistor502 and to a drain of the transistor 602. Sources of the transistors 601and 602 are connected to the ground. A gate of the transistor 601 isconnected to the reception signal input terminal IN_(RX) of thehigh-frequency amplifier 501 a. The gate of the transistor 601 is alsoconnected to a common terminal of the transmission/reception selectorswitch SW1 through the resistor R1. One of two terminals of the switchSW1 is connected to the ground, while the other terminal is connected tothe positive side power supply terminal of the DC power supply Vbias1.

A gate of the transistor 602 is connected to the transmission signalinput terminal IN_(TX) of the high-frequency amplifier 501 a. The gateof the transistor 602 is also connected to a common terminal of thetransmission/reception selector switch SW2 through the resistor R2. Oneof two terminals of the switch SW2 is connected to the ground, while theother terminal is connected to the positive side power supply terminalof the DC power supply Vbias2.

The negative side power supply terminals of the DC power supplies Vbias1and Vbias2 are connected to the ground. Further, an output node OUT2outputs a signal toward the inside of the semiconductor integratedcircuit, separated from the original output terminal OUT.

During the reception mode, transmission/reception switching controlsignals from the control unit 50 shown in FIG. 5 are input to thetransmission/reception switching control terminal S1 and to thetransmission/reception switching control terminal S2, and the switch SW1is connected to the terminal on the bias DC power supply Vbias1 side,and thereby the transistor 601 turns on, while the switch SW2 isconnected to the terminal on the ground side, and thereby the transistor602 turns off.

In the transmission mode, the states of the switches SW1 and SW2 and thestates of the transistors 601 and 602 are inverted from those in thereception mode. The transmission/reception selector switches SW1 and SW2may have other constructions than those mentioned above so long as theycan turn on/off the transistors 601 and 602, respectively.

FIG. 7 is a diagram illustrating a rough layout of the high-frequencyamplifier 501 a shown in FIG. 6 which is fabricated in an ordinary CMOSprocess. In FIG. 7, GND indicates the source of the transistor 602. Thesame reference numerals as those shown in FIG. 6 denote the same orcorresponding elements.

In the layout shown in FIG. 7, the area occupied by the spiral inductorhaving an inductance of 6 nH is 0.16 mm², and the area of the layout ofthe high-frequency amplifier is 0.35 mm². Although the spiral inductoroccupies 46% of the entire layout area, the area of the high-frequencyamplifier 501 a according to the second embodiment can reduce to 58% incomparison with the conventional example shown in FIG. 12. This areareduction effect can be achieved in all the high-frequency amplifiersaccording to the first and second embodiments of the invention.

FIG. 8 shows the construction of a high-frequency amplifier 501 b whichis a second example of the high-frequency amplifier 501 according to thesecond embodiment.

In FIG. 8, the high-frequency amplifier 501 b is obtained by newlyadding a transmission signal output terminal OUT_(TX) and a switch SW6to the above-mentioned high-frequency amplifier 501 a shown in FIG. 6.The switch SW6 is connected between the transmission signal outputterminal OUT_(TX) and the output terminal OUT_(RX) (corresponding to theOUT2 in FIG. 6).

During the reception mode, the switch SW6 is opened, and the amplifiedreception signal is outputted from the output terminal OUT_(RX). Duringthe transmission mode, the switch SW6 is short-circuited, and theamplified transmission signal is outputted from the transmission signaloutput terminal OUT_(TX).

As described above, according to the second embodiment, two spiralinductors to be connected as loads between the power supply terminal andthe output terminal of the low-noise amplifier that amplifies areception signal when performing communication by the time-divisionduplex scheme and between the power supply terminal and the outputterminal of the power amplifier that amplifies the transmission signal,are unified, and the cascade stage transistor is provided. Therefore,when the high-frequency amplifier is constituted as an integratedcircuit, the ratio of the spiral inductor to the substrate area of theintegrated circuit can be reduced, and thereby the integrated circuitcan be miniaturized, resulting in a high-frequency amplifier that can bemanufactured at reduced cost and has less parasitic capacitance at theoutput terminal.

While in this second embodiment the high-frequency amplifier 501includes two transmission/reception switching control terminals, thehigh-frequency amplifier may include at least one transmission/receptionswitching control terminal so long as it can perform operationalswitching between the reception signal amplifying part 102 and thetransmission signal amplifying part 103.

Further, while the switch SW6 has one transmission/reception switchingcontrol terminal (S1 or S2), the switch SW6 may have twotransmission/reception switching control terminals (S1 and S2).

Further, in this second embodiment, inductors may be used in place ofthe resistors R1 and R2.

Further, while in this second embodiment the high-frequency amplifier501 amplifies a single-phase transmission signal and a single-phasereception signal, two pieces of high-frequency amplifiers 501 may beprovided to amplify a differential transmission signal and adifferential reception signal.

Further, in the reception signal amplifying part, in order to achievematching of either or both of noise and gain, an inductor, or aresistor, or a capacitor may be connected to either or both of the gateand source of the NMOS transistor.

Further, while in this second embodiment the reception signal amplifyingpart 102 and the transmission signal amplifying part 103 include onlythe NMOS transistors, the polarity of the circuit may be inverted. Thatis, the reception signal amplifying part 102 and the transmission signalamplifying part 103 may be constituted as high-frequency amplifiersincluding only PMOS transistors.

Further, the transistors described in this second embodiment may beimplemented by any of MOSFETs, MESFETs, JFETs, HEMTs, bipolar junctiontransistors, and heterojunction transistors, or a combination of some ofthese transistors.

Further, the transistors described in this second embodiment may beimplemented by any of silicon, silicon-germanium, and III-V compoundsemiconductor.

Furthermore, the spiral inductor 104 according to the second embodimentincludes inductors in the integrated circuit and in a package or moduleincluding the integrated circuit. The point is that the high-frequencyamplifier 501 should be constituted such that the reception signalamplifying part 102 and the transmission signal amplifying part 103share one inductor as a common load, a switch for alternately selectingon and off of the reception signal amplifying part 102 and thetransmission signal amplifying part 103 is provided, and cascadetransistors are connected between the inductor and the outputs of thereception signal amplifying part 102 and the transmission signalamplifying part 103, respectively.

Embodiment 3

FIG. 9 shows the construction of a transmission/reception system 901according to a third embodiment of the present invention.

The transmission/reception system 901 shown in FIG. 9 includes ahigh-frequency amplifier 501 b which is identical to that of the secondembodiment.

In FIG. 9, the transmission/reception system 901 comprises atransmission/reception integrated circuit for communication 902, anantenna 903, an RF filter 904, a transmission/reception selector switch905, an input matching circuit 906, and an output matching circuit 907.

The communication transmission/reception integrated circuit 902comprises a high-frequency amplifier 501 b which is identical to that ofthe second embodiment, a reception mixer 908, a transmission mixer 909,a frequency synthesizer 910, a reception filter 911, a transmissionfilter 912, an A/D converter (hereinafter referred to as “ADC”) 913, aD/A converter (hereinafter referred to as “DAC”) 914, and a digitalsignal processor (hereinafter referred to as “DSP”) 915.

Next, the operation will be described.

In the time division duplex scheme, in response to a timing of switchingbetween signal transmission and reception, the transmission/receptionselector switch 905 and the high-frequency amplifier 501 b arecontrolled by a transmission/reception switching signal from the DSP915. The transmission/reception switching signal may be generated by acontrol circuit other than the DSP, as shown in FIG. 1.

During the reception, a signal received by the antenna 903 is input tothe high-frequency amplifier 501 b through the RF filter 904, thetransmission/reception selector switch 905, and the input matchingcircuit 906. The reception signal amplified by the high-frequencyamplifier 501 b is input to the reception mixer 908.

The reception mixer 908 mixes the reception signal outputted from thehigh-frequency amplifier 501 b and an oscillation signal outputted fromthe frequency synthesizer 910. The output of the reception mixer 908 issupplied to the ADC 913 through the reception filter 911. The ADC 913converts the analog reception signal outputted from the reception filter911 into a digital reception signal. The DSP 915 processes the digitalreception signal.

Next, during the transmission, the digital transmission signal processedby the DSP 915 is converted into an analog transmission signal by theDAC 914. The analog transmission signal is input to the transmissionmixer 909 through the transmission filter 912. The transmission mixer909 mixes the transmission signal outputted from the transmission mixer909 and the oscillation signal outputted from the frequency synthesizer910.

The high-frequency amplifier 501 b amplifies the output of thetransmission mixer 909. The amplified transmission signal is transmittedthrough the output matching circuit 907, the transmission/receptionselector switch 905, and the RF filter 904, and outputted from theantenna 903.

As described above, since the high-frequency amplifier 501 b identicalto that of the second embodiment is used as a transmission/receptionsignal amplifier, the areas of the high-frequency amplifier 501 b andthe transmission/reception integrated circuit for communication 902 arereduced and thereby the cost is reduced, resulting in thetransmission/reception system 901 with reduced production cost. Ahigh-frequency amplifier 101 c identical to that of the first embodimentmay be used instead of the high-frequency amplifier 501 b.

FIG. 10 shows the construction of a transmission/reception system 901 aas a second example of the transmission/reception system 901 accordingto the third embodiment.

The transmission/reception system 901 a shown in FIG. 10 includes ahigh-frequency amplifier 501 a which is identical to that of the secondembodiment.

The transmission/reception system 901 a shown in FIG. 10 and thetransmission/reception system 901 shown in FIG. 9 are different fromeach other in the constructions of the transmission/reception integratedcircuit for communication 902 and the transmission/reception integratedcircuit for communication 1001.

The transmission/reception integrated circuit for communication 1001comprises transmission/reception selector switches 1002 and 1003, ahigh-frequency amplifier 501 a according to the second embodiment, areception mixer 908, a transmission mixer 909, a frequency synthesizer910, a reception filter 911, a transmission filter 912, an ADC 913, aDAC 914, and a DSP 915.

The transmission/reception selector switch 1002 is turned on in thereception mode, and turned off in the transmission mode. Thetransmission/reception selector switch 1003 performs an operationreverse to the transmission/reception selector switch 1002. Otheroperations are identical to those mentioned with reference to FIG. 9.

As described above, according to the third embodiment, thetransmission/reception system is constituted by using the high-frequencyamplifier in which two spiral inductors to be connected as loads betweenthe power supply terminal and the output terminal of the low-noiseamplifier that amplifies a reception signal when performingcommunication by the time-division duplex scheme and between the powersupply terminal and the output terminal of the power amplifier thatamplifies the transmission signal, are unified, and the cascade stagetransistor is provided. Therefore, when the transmission/receptionsystem is constituted as an integrated circuit, the ratio of the spiralinductor to the substrate area of the integrated circuit can be reduced,and thereby the integrated circuit can be miniaturized, resulting in atransmission/reception system which can be manufactured at reduced cost,and has less parasitic capacitance at the output terminal of thehigh-frequency amplifier.

The high-frequency amplifiers 101 a and 101 b may be used instead of thehigh-frequency amplifiers 501 a and 501 b, respectively. The point isthat a transmission/reception system to be used for time-division duplexcommunication should be constituted by using the high-frequencyamplifier described for the first embodiment or the second embodiment.

Embodiment 4

By the way, in recent years, a high-speed transmission technique forradio communication, which is called MIMO (Multiple Input MultipleOutput), has been developed, and it has already been put to practicaluse in some fields such as radio LAN equipment. The MIMO is a techniquefor performing transmission/reception of data by using plural antennasin both of a transmitter and a receiver.

In the MIMO, data to be transmitted is divided into plural data totransmit the data in parallel, i.e., simultaneously, in space by usingplural antennas for one frequency band, and the data received by pluralantennas are synthesized and decoded, whereby the communication speed issignificantly increased, and the communication status is significantlyimproved under an environment where many obstacles exist, such asindoor.

That is, at the transmitter side of the MIMO, a transmission signal issubjected to space-time coding (STC) to perform recombination of data inboth regions of time and space, and thereafter, radio waves areoutputted from the plural antennas.

At the receiver side of the MIMO, the radio waves that have propagatedthrough a multipath transmission line are received by plural antennas,and space-time decoding (STD) which is a process reverse to the STC isperformed, whereby interferences are removed from the plural signals,and the respective signals are separated and synthesized to output areception signal.

FIG. 13 shows the construction of a high-frequency amplifier 1301according to the fourth embodiment.

The high-frequency amplifier 1301 shown in FIG. 13( a) comprises twohigh-frequency amplifiers 1301 a and 1301 b each having a receptionsignal amplifying part and a transmission signal amplifying part whichare constituted as mentioned for the first embodiment.

In FIG. 13( a), the high-frequency amplifiers 1301 a, 1301 b havereception signal amplifying parts 1302 a, 1302 b, transmission signalamplifying parts 1303 a, 1303 b, spiral inductors 1304 a, 1304 b, andoutput terminals OUTa, OUTb, respectively.

The reception signal amplifying parts 1302 a, 1302 b havetransmission/reception switching control terminals S1 a, S1 b, andreception signal input terminals IN_(RX)a, IN_(RX)b, respectively. Thetransmission signal amplifying parts 1303 a, 1303 b havetransmission/reception switching control terminals S2 a, S2 b, andtransmission signal input terminals IN_(TX)a, IN_(TX)b, respectively.

The reception signal amplifying parts 1302 a, 1302 b and thetransmission signal amplifying parts 1303 a, 1303 b are connected to DCpower supplies VDDa, VDDb through the spiral inductors 1304 a, 1304 b,respectively.

FIG. 13( b) shows the specific construction of FIG. 13( a). Thehigh-frequency amplifiers 1301 a and 1301 b have the same constructionas that of the high-frequency amplifier 501 b shown in FIG. 8. In FIG.13( b), suffixes a, b are added to the constituents of the respectivehigh-frequency amplifiers.

In the high-frequency amplifier 1301 thus constructed, by operating bothof the high-frequency amplifiers 1301 a and 1301 b as transmissionsignal amplifiers or reception signal amplifiers, the high frequencyamplifier can be operated as a transmission signal amplifier or areception signal amplifier of the MIMO system.

Further, when one of the high-frequency amplifiers 1301 a and 1301 b isoperated as a transmission signal amplifier while the other is operatedas a reception signal amplifier, the high-frequency amplifier can beoperated as a transmission/reception high-frequency amplifier of a FDD(Frequency Division Duplex) system.

An FDD system transceiver divides a frequency band to be used into afrequency band for transmission and a frequency band for reception torealize simultaneous execution of transmission and reception. Handyphones excluding PHS (Personal Handyphone System) adopt the FDD system.

FIG. 14 shows a transmission/reception system according to the fourthembodiment. FIGS. 14( a) and 14(b) show the cases where thehigh-frequency amplifier according to the fourth embodiment is operatedas a MIMO transceiver 1401 a and an FDD transceiver 1401 b,respectively.

The MIMO transceiver shown in FIG. 14( a) has two transmission/receptionsystems 901 a and 901 b which are constituted as shown in FIG. 9. InFIG. 14( a), suffixes a, b are added to the constituents of therespective transmission/reception systems.

In the MIMO transceiver, transmission/reception selector switches 905 aand 905 b are controlled so that both of the two transmission/receptionsystem 901 a and 901 b perform reception or transmission. The twotransmission/reception integrated circuits for communication 902 a and902 b share a DSP. The shared DSP 915 d performs STD to the receptiondigital signals obtained from ADCs 913 a and 913 b in the twotransmission/reception integrated circuits for communication 902 a and902 b, and performs STC to the transmission digital signals to be inputto the DACs 914 a and 914 b, respectively.

The two transmission/reception integrated circuits for communication 902a and 902 b are contained in a package 901 d. Further, the twotransmission/reception systems 901 a and 901 b may be constituted as anintegrated circuit.

The FDD transceiver shown in FIG. 14( b) has two transmission/receptionsystems 901 a and 901 b which are constituted as shown in FIG. 9. InFIG. 14( a), suffixes a, b are added to the constituents of therespective transmission/reception systems.

In the FDD transceiver, transmission/reception selector switches 905 aand 905 b are controlled so that one of the two transmission/receptionsystems 901 a and 901 b performs reception while the other performstransmission.

As described above, according to the fourth embodiment, twohigh-frequency amplifiers having the same construction as that of thefirst embodiment are provided in a single transmission/receptionapparatus, and both of the two high-frequency amplifiers are operated astransmitters or receivers, or one of the two high-frequency amplifiersis operated as a transmitter while the other is operated as a receiver,whereby the single transmission/reception apparatus can be operated aseither a MIMO system transceiver or an FDD system transceiver.

To be specific, two high-frequency amplifiers are provided in onetransmission/reception apparatus, each amplifier having such aconstruction that two spiral inductors to be connected as loads betweenthe power supply terminal and the output terminal of the low-noiseamplifier that amplifies a reception signal when performingcommunication by the time-division duplex scheme and between the powersupply terminal and the output terminal of the power amplifier thatamplifies the transmission signal, are unified. When both of the twohigh-frequency amplifiers are operated as transmitters or receivers,these amplifiers can be operated in the MIMO system which enables anincrease in the communication speed. On the other hand, when one of thetwo high-frequency amplifiers is operated as a transmitter while theother is operated as a receiver, these amplifiers can be operated in theFDD system which enables simultaneous execution of transmission andreception. While in this fourth embodiment two high-frequency amplifiersare provided, three or more high-frequency amplifiers may be provided.

Further, while in this fourth embodiment the construction of thehigh-frequency amplifier body is identical to that shown in FIG. 8, itmay be identical to any of those shown in FIGS. 2, 3(a), 4, and 6.

Embodiment 5

A fifth embodiment of the present invention makes up for a deficiency incapacitance at an output terminal OUT of a high-frequency amplifierwhich is constituted similarly to that of the second embodiment shown inFIG. 8.

FIG. 15( a) shows the construction of a high-frequency amplifier 501 cwhich is a first example of a high-frequency amplifier 501 according tothe fifth embodiment.

In FIG. 15( a), CF denotes a parasitic capacitance at the outputterminal OUT, and Vc denotes a variable capacitance element placedbetween the output terminal OUT and the ground.

When this high-frequency amplifier 501 c is used as a transceiver ofradio LAN, it is necessary to set its resonance frequency to 2.4 GHz.Since a resonance frequency f0 can be obtained by f0=1/(2π(LC)^(0.5)), acapacitance C needed for obtaining a desired resonance frequency f0 canbe obtained by C=1/(L(2πf0)²).

By the way, while a parasitic capacitance CF occurs between the groundand the node N at which the output terminal OUT, the spiral inductor104, the transistor 502, and the switch SW5 are connected each other,the capacitance value of this parasitic capacitance is sometimesinsufficient to obtain the above-mentioned resonance frequency of 2.4GHz.

So, a variable capacitance element Vc is provided between the node N andthe ground, and the capacitance value of the variable capacitanceelement is varied to make up for the deficiency in the parasiticcapacitance, thereby obtaining the desired resonance frequency.

FIG. 15( b) shows the construction of a high-frequency amplifier 501 dwhich is a second example of the high-frequency amplifier 501 accordingto the fifth embodiment of the present invention.

In this second example, series-connected bodies each comprising a fixedcapacitance and a switch are connected between the node N and theground, instead of the variable capacitance element according to thefirst example.

In FIG. 15( b), CA1 and SA1, CA2 and SA2, CA3 and SA3 areseries-connected capacitances and switches, respectively, and the threeseries-connected bodies comprising these capacitances and switches arerespectively connected between the node N and the ground.

For example, a relationship of CA1>CA2>CA3 is established among thevalues of the capacitances CA1, CA2, and CA3.

In this case, when the parasitic capacitance and the capacitance CA1 arenot sufficient to obtain the above-mentioned resonance frequency, theswitch SA2 is closed to add the capacitance CA2. If, even in this state,the capacitance value to obtain the desired resonance frequency is notachieved, the switch SA3 is closed to add the capacitance CA3.

In this way, the capacitance to be added to the parasitic capacitancevalue is varied in stages by appropriately selecting the switches SA1,SA2, and SA3, thereby obtaining the desired resonance frequency.

Further, FIG. 15( c) shows the construction of a high-frequencyamplifier 501 e as a third example of the high-frequency amplifier 501according to the fifth embodiment.

In this third example, a capacitance CA having a predeterminedcapacitance value is connected between the node N and the ground.

If the value of the parasitic capacitance CF that occurs at the node Nis known by such as measuring the value in advance, it is possible tocalculate a capacitance value corresponding to a deficiency in thecapacitance required to obtain the desired resonance frequency.

Accordingly, the deficient capacitance value is incorporated as thecapacitance CA, thereby obtaining the high-frequency amplifier 501 ethat does not require adjustment of the capacitance value to be added,which amplifier is suitable for mass production.

As described above, according to the fifth embodiment, when a desiredresonance frequency cannot be obtained by only the capacitance value ofthe parasitic capacitance that occurs at the node N, a capacitanceelement having a capacitance value corresponding to the deficiency isconnected to the node N. Therefore, a deficiency in the capacitancerequired to obtain the desired resonance frequency is appropriated,thereby obtaining a high-frequency amplifier having the desiredresonance frequency.

While in this fifth embodiment the construction of the high-frequencyamplifier body is identical to that shown in FIG. 8, it may be identicalto any of those shown in FIGS. 2, 3, 3(a), 4, and 6.

Embodiment 6

In a sixth embodiment of the present invention, a construction foradjusting a bias voltage is provided at the input side of ahigh-frequency amplifier that is identical to the second embodiment.

FIG. 16( a) shows a first example of the high-frequency amplifieraccording to the sixth embodiment. With reference to FIG. 16( a),switches SW6 and SW7 are provided between the gates of transistors 801and 802 and the ground, respectively, so that the switches SW6 and SW7are turned on when the switches SW1 and SW2 are placed at the groundside, and turned off when the switches are placed at the bias powersupply side.

Assuming that these switches SW6 and SW7 do not exist, when the switchesSW1 and SW2 select the ground side, the gate voltages of the transistors801 and 802 become higher than the ground voltage because the resistorsR1 and R2 exist.

On the other hand, in the construction shown in FIG. 16( a) having theswitches SW6 and SW7, since the switches SW6 and SW7 are turned onsimultaneously with the switches SW1 and SW2, the gates of thetransistors 801 and 802 of the high-frequency amplifier 501 can bereliably fixed to the ground voltage.

FIG. 16( b) shows a second embodiment example of the high-frequencyamplifier according to the sixth embodiment. In FIG. 16( b), variablevoltage supplies Vvr1 and Vvr2 that can vary voltage are disposedbetween the ground and the ground side terminals of the resistors R1 andR2, respectively, and a switch SW8 is disposed between the ground andthe ground side terminals of the resistors R1 and R2.

A faint radio wave received by the antenna is input to the gate of thetransistor 801, and when this radio wave is amplified by thehigh-frequency amplifier 501 g, the current that flows in the transistor801 is increased by increasing the voltage of the variable voltagesupply Vvr2, and the current that flows in the transistor 802 isdecreased by lowering the voltage of the variable voltage supply Vvr2,thereby setting the transmission signal amplifying part 103 in anoperation state close to the halting state.

For example, the gate-to-source voltage of the transistor 802 is set to0.4V˜0.5V by adjusting the variable voltage supply Vvr2 so as to operatethe transmission signal amplifying part 103 in the state where currenthardly flows in the transistor 802, whereby the amplification can becarried out at lower noise relative to the case where only the receptionsignal amplifying part 102 is operated.

Further, as performances of a high-frequency amplifier, especially, afront end which is an amplifier directly connected to an antenna, thereare performance as to how large amplitude of a signal the amplifier canreceive, as well as performance as to how much extent the amplifier canamplify a faint signal. When a signal of a large amplitude is input tothe reception signal amplifying part 102, the gain of the amplifyingpart 102 is suppressed by short-circuiting the switch SW8, and therebythe large-amplitude input signal can be amplified without saturating thesame.

For example, as shown in FIG. 16( c), when a reception signal amplitudedetection unit 70 detects that a large-amplitude reception signal isinputted, the switch SW8 is short-circuited, whereby the input signalbypasses the high-frequency amplifier 501 g and is amplified only by thenext-stage high-frequency amplifier 501 g 1, thereby the large-amplitudeinput signal can be amplified without saturation.

As described above, according to the sixth embodiment, since the biasvoltage at the input side of the high-frequency amplifier is adjustable,a reduction in noise of the high-frequency amplifier can be realized bysetting the bias voltage such that, during the reception mode, thereception signal amplifying part constituting the high-frequencyamplifier is set in the normal operation state while the transmissionsignal amplifying part is set in the operation state that is almostclose to the off state. Further, when a large-amplitude signal isinputted, the input signal is passed through the inside of thehigh-frequency amplifier, whereby saturation is avoided and performanceof the high-frequency amplifier is enhanced. Further, a switch forshort-circuiting the input of the high-frequency amplifier to the groundis provided, whereby reliable grounding of the input signal can beachieved.

While in the sixth embodiment the construction of the high-frequencyamplifier body is identical to that shown in FIG. 8, it may be identicalto any of those shown in FIGS. 2 and 6.

Embodiment 7

A seventh embodiment of the present invention is constituted such thatinput and output of a high-frequency amplifier can be performed by oneterminal.

FIG. 17( a) shows a first example of the high-frequency amplifieraccording to the seventh embodiment.

FIG. 17( a) shows a high-frequency amplifier 101 c that is identical tothe construction shown in FIG. 4 according to the first embodiment.

In the high-frequency amplifier shown in FIG. 17( a), when the switchesSW3 and SW4 are placed to the ground side and the bias power supplyside, respectively, according to the transmission/reception switchingsignals applied to the transmission/reception switching controlterminals S1 and S2, the transistor 304 is turned on and the transistor302 is turned off, whereby the transmission signal amplified by thetransmission signal amplifying part 103 can be output to the IOterminal.

Inversely, when the switches SW3 and SW4 are placed to the bias powersupply side and the ground side, respectively, the signal received bythe reception signal amplifying part 102 can be inputted.

The node to which the output terminal OUT_(TX) of the switch SW5 of thethus constituted high-frequency amplifier should be connected (i.e., thenode on the opposite side from the spiral inductor 104), and the node towhich the input terminal IN_(RX) of the amplification transistor 301should be connected (i.e., the gate node) are connected to the IOterminal via the capacitances C1 and C2, respectively, whereby the inputand output terminals are unified.

In the high-frequency amplifier thus constituted, when amplifying thetransmission signal, the switch SW4 of the transmission signalamplifying part 103 is set to the bias power supply side, and the switchSW5 is closed. Thereby, the transmission signal amplified by thetransistor 303 is transmitted through the transistor 304, the switchSW5, and the capacitance C1 and outputted from the IO terminal to theoutside.

At this time, the switch SW3 of the reception signal amplifying part 102is set to the ground side. Therefore, even when the amplifiedtransmission signal is input to the reception signal amplifying part 102through the capacitance C2, since the transistor 302 is in the offstate, overlapping with the amplified transmission signal does notoccur.

Further, when amplifying the reception signal, the switch SW3 of thereception signal amplifier 102 is set to the bias power supply side, andthe switch SW5 is opened. Thereby, the reception signal that is inputtedfrom the IO terminal through the capacitance C2 is amplified by thetransistor 301, and the amplified signal is outputted from the outputterminal OUT through the transistor 302.

At this time, since the switch SW4 of the transmission signal amplifyingpart 103 is set to the ground side, the transistor 304 is in the offstate even when the transmission signal is input to the transistor 303.Therefore, overlapping with the amplified reception signal does notoccur.

Further, FIG. 17( b) shows a second example of a high-frequencyamplifier according to a seventh embodiment.

FIG. 17( b) has a high-frequency amplifier 501 b which is identical tothat shown in FIG. 8 according to the second embodiment.

However, like in FIG. 17( a), the node to which the output terminalOUT_(TX) of the switch SW5 should be connected and the node to which theinput terminal IN_(RX) of the transistor 801 should be connected areconnected to the IO terminal via the capacitances C1 and C2,respectively.

Since the high-frequency amplifier is constructed as described above,when the entire apparatus is constituted as an integrated circuit, thenumber of the terminals can be reduced by one, and the switch SW5 to beexternally connected to the chip can be dispensed with.

As described above, according to the seventh embodiment, the outputterminal for outputting the signal from the transmission signalamplifying part to the outside, and the input terminal for inputting thesignal to the reception signal amplifying part are connected via acapacitance to consolidate the terminals as a common input/outputterminal. Therefore, when the entire apparatus is constituted as anintegrated circuit, one terminal can be dispensed with, therebyrealizing cost reduction. Alternatively, the unnecessary terminal can beused for input/output of another signal.

While in this seventh embodiment the construction of the high-frequencyamplifier body is identical to that shown in FIG. 4 or 8, it may beidentical to any of those shown in FIGS. 13( b), 15(a), 15(b), 15(c),16(a), and 16(b).

APPLICABILITY IN INDUSTRY

As described above, a high-frequency amplifier and atransmission/reception system according to the present invention canreduce an area to be occupied by inductors when these devices aremounted on an integrated circuit, and therefore, are effective inreducing production costs.

1. A high-frequency amplifier including: a reception signal amplifyingpart, a transmission signal amplifying part which is separate anddistinct from the reception signal amplifying part, and an inductor;said reception signal amplifying part having a reception signal inputterminal, and a first transmission/reception switching control terminal;said transmission signal amplifying part having a transmission signalinput terminal, and a second transmission/reception switching controlterminal; and a common output terminal to which an output of thereception signal amplifying part and an output of the transmissionsignal amplifying part are connected; wherein, switching of operationsof the reception signal amplifying part and the transmission signalamplifying part is carried out such that, during a reception mode,control signals are input to the first transmission/reception switchingcontrol terminal and to the second transmission/reception switchingcontrol terminal, whereby the transmission signal amplifying part isturned off, and the reception signal amplifying part is turned on toamplify a reception signal that is inputted from the reception signalinput terminal, and during a transmission mode, control signals areinput to the first transmission/reception switching control terminal andto the second transmission/reception switching control terminal, wherebythe reception signal amplifying part is turned off, and the transmissionsignal amplifying part is turned on to amplify a transmission signalthat is inputted from the transmission signal input terminal; and saidinductor is connected between a DC power supply terminal and the commonoutput terminal as a load that is common to the reception signalamplifying part and the transmission signal amplifying part.
 2. Ahigh-frequency amplifier as defined in claim 1 further including aswitch and a transmission signal output terminal, wherein said switch isconnected between the output terminal and the transmission signal outputterminal; during the reception mode, said switch is turned off, wherebythe reception signal inputted from the reception signal input terminalis amplified and transmitted to the output terminal; and during thetransmission mode, said switch is turned on, whereby the transmissionsignal inputted form the transmission signal input terminal is amplifiedand transmitted to the transmission signal output terminal.
 3. Ahigh-frequency amplifier as defined in claim 1 wherein said receptionsignal amplifying part has a transistor for amplifying the receptionsignal.
 4. A high-frequency amplifier as defined in claim 3 wherein saidtransistor of said reception signal amplifying part is optimized torealize noise matching.
 5. A high-frequency amplifier as defined inclaim 3 wherein said transistor of said reception signal amplifying partis optimized to realize gain matching.
 6. A high-frequency amplifier asdefined in claim 1 wherein said transmission signal amplifying part hasa transistor for amplifying power.
 7. A high-frequency amplifier asdefined in claim 1 wherein said inductor comprises a spiral inductorthat is mounted in an integrated circuit.
 8. A high-frequency amplifieras defined in claim 1 wherein said reception signal amplifying part,said transmission signal amplifying part, and said inductor are mountedon the same integrated circuit.
 9. A high-frequency amplifier as definedin claim 1 wherein said inductor comprises a spiral inductor that ismounted in a module.
 10. A high-frequency amplifier comprising twopieces of high-frequency amplifiers defined in claim 1, and amplifying adifferential reception signal and a differential transmission signal.11. A high-frequency amplifier as defined in claim 1 wherein each oftransistors constituting the high-frequency amplifier is any of aMOSFET, a MESFET, a JFET, a HEMT, a bipolar junction transistor, and aheterojunction transistor, or a combination of some of thesetransistors.
 12. A high-frequency amplifier as defined in claim 1wherein each of transistors constituting the high-frequency amplifiercomprises any of silicon, silicon-germanium, and III-V compoundsemiconductor.
 13. A high-frequency amplifier as defined in claim 1wherein said reception signal amplifying part has a transistor foramplifying the reception signal, and a first variable voltage supplythat can vary a voltage applied between a gate of the transistor and theground; said transmission signal amplifying part has a transistor foramplifying power, and a second variable voltage supply that can vary avoltage applied to a gate of the transistor and the ground; said firsttransmission/reception switching control terminal is connected to thefirst variable voltage supply; said second transmission/receptionswitching control terminal is connected to the second variable voltagesupply; during the reception mode, control signals are input to thefirst transmission/reception switching control terminal and to thesecond transmission/reception switching control terminal, whereby thetransmission signal amplifying part is almost turned off, and thereception signal amplifying part is turned on to amplify the receptionsignal inputted from the reception signal input terminal at low noise.14. A high-frequency amplifier as defined in claim 1 including a switchdisposed between the output terminal and the reception signal inputterminal, and said switch being turned on when the reception signal hasa large amplitude.
 15. A high-frequency amplifier as defined in claim 1wherein when a capacitance that is required between the output terminaland the ground by the high-frequency amplifier is deficient due to aparasitic capacitance at the output terminal, a capacitance having acapacitance value corresponding to the deficit is connected.
 16. Ahigh-frequency amplifier as defined in claim 1 including switchesdisposed between the reception signal input terminal, the transmissionsignal input terminal and the ground, respectively, and the switch whichis disposed at the side where the reception signal amplifying part orthe transmission signal amplifying part is turned off, is turned on. 17.A high-frequency amplifier as defined in claim 1 further including aswitch, an input/output terminal, and first and second capacitances,wherein a series-connected body comprising said switch and said firstcapacitance is connected between a node to which the output terminal isconnected, and the input/output terminal; said input/output terminal isconnected through the second capacitance to a node to which thetransmission signal input terminal should be connected; during thereception mode, said switch is turned off, and the reception signalinputted to the input/output terminal is amplified and transmitted tothe output terminal; and during the transmission mode, said switch isturned on, and the transmission signal inputted from the transmissionsignal input terminal is amplified and transmitted to the input/outputterminal.
 18. A transmission/reception system including atransmission/reception unit for transmitting and receiving ahigh-frequency signal, said system including a high-frequency amplifieras defined in claim 1, and operating in a time-division duplexcommunication scheme.
 19. A transmission/reception system having atransmission/reception unit for transmitting and receiving ahigh-frequency signal, said system including a plurality ofhigh-frequency amplifiers as defined in claim 1, and being able to setwhether said plural high-frequency amplifiers are simultaneouslyswitching between the transmission mode and the reception mode, or someof them are in the transmission mode while the others are in thereception mode.
 20. A high-frequency amplifier including a receptionsignal amplifying part, a transmission signal amplifying part which isseparate and distinct from the reception signal amplifying part, aninductor, and a transistor, wherein: said reception signal amplifyingpart has a reception signal input terminal, and a firsttransmission/reception switching control terminal; said transmissionsignal amplifying part has a transmission signal input terminal, and asecond transmission/reception switching control terminal; an output ofthe reception signal amplifying part and an output of the transmissionsignal amplifying part are connected to the transistor; switching ofoperations of the reception signal amplifying part and the transmissionsignal amplifying part is carried out such that, during a receptionmode, control signals are input to the first transmission/receptionswitching control terminal and to the second transmission/receptionswitching control terminal, whereby the transmission signal amplifyingpart is turned off, and the reception signal amplifying part is turnedon to amplify a reception signal that is inputted from the receptionsignal input terminal, and during a transmission mode, control signalsare input to the first transmission/reception switching control terminaland to the second transmission/reception switching control terminal,whereby the reception signal amplifying part is turned off, and thetransmission signal amplifying part is turned on to amplify atransmission signal that is inputted from the transmission signal inputterminal; said inductor is connected between a DC power supply terminaland the transistor as a load that is common to the reception signalamplifying part and the transmission signal amplifying part; and anoutput terminal is provided at a connection point of the inductor andthe transistor.